A discrete channel filter of a type used in communications transmission equipment requires a crystal network device which includes a plurality of elongated crystal resonator plates of different resonant frequencies connected in parallel. In a known crystal network device utilizing two sets of two of the crystal resonator plates, each crystal resonator plate is supported by four lead wires (two on each side of the plate) bonded to electrodes of the plate and soldered to individual conductive paths on a short thin section of printed wiring board, known as a "rail." A molded plastic holder includes shelves for supporting the rails, and further includes essentially planar, slightly tapered side fins which extend adjacent the crystal resonator plates to provide physical protection. Each set of the crystal resonator plates and its associated rails are mounted on the top and bottom sides of the molded plastic holder, respectively. The rails are attached by electrically conductive epoxy cement to terminal studs which are press-fitted into apertures in the holder, and which project from the holder for mounting the assembly on a printed circuit board and electrically connecting the crystal resonator plates to circuits on the board.
In the above-described crystal network device, each crystal resonator plate, together with its lead support wires and printed circuit board rails, forms a subassembly device which can be individually tuned. However, since the printed circuit board rails do not provide a fixed mounting structure until the rails are bonded to the terminal studs, measurements of the frequency of the subassembly made in intermediate stages of its fabrication may be inaccurate and subject to variations. Further, strain-free joints between the rails and the terminal studs are difficult to achieve because the electrically conductive epoxy cement used must be cured at an elevated temperature, and is subject to fracturing, causing electrical opens and/or other defects. In addition, since the crystal network device must be fabricated to form a non-separable structure before final test measurements of the device are made, a final device not meeting test requirements generally requires difficult and expensive repair, or may have to be scrapped in its entirety.
Accordingly, a purpose of this invention is to provide a crystal network device consisting of separate crystal resonator devices which can be pretested and then assembled to form a crystal network device having a rigid composite structure, with the resultant crystal network device being capable of ready disassembly, if necessary.